MHD studies towards simulating White Dwarf Mergers using Castro Mar - - PowerPoint PPT Presentation

MHD studies towards simulating White Dwarf Mergers using Castro

Mar´ ıa G. Barrios Sazo

Stony Brook University

Castro

Castro is an AMR code that solves the compressible hydrodynamic equations for astrophysical flows

◮ conservation of mass ∂ρ

∂t = −∇ · (ρu

u u) + Sext,ρ

◮ conservation of momentum ∂(ρu

u u) ∂t

= −∇ · (ρu u uu u u) − ∇p + ρg g g + Sext,ρu

u u

◮ conservation of total energy

∂(ρE) ∂t

= −∇ · (ρu u uE + pu u u) + ρHnuc + ρu u u · g g g + Sext,ρE

User can supply EOS and reaction networks Self gravity Radiation, gray and multigroup FLD Supports 1-d, 2-d and 3-d

Castro

Zingale et al. 2017

4 2 2 4 x (km) ×104 4 2 2 4 y (km) ×104 10−1 100 101 102 103 104 105 106 107 ρ

g cm3

• WD merger showing 2-level grid

structure Adaptive Mesh Refinement, built on AMReX Simultaneous refinement in space and time Hybrid parallelism, MPI+OpenMP Regression tests Ongoing development for GPUs Open Source github.com/AMReX-Astro/Castro

Scaling

NERSC Cori

101 102 number of nodes 100 101 102

• avg. time / step

10000 20000 30000 40000 50000 60000 number of threads

Castro 3-d wdmerger (hydro + Poisson gravity) 2563 gnu 2563 intel 5123 gnu 5123 intel no AMR base + one 4x level

Zingale et al. 2017

OLCF Titan

102 103 104 number of cores 100 101 102

• avg. time / step

Castro 3-d wdmerger (hydro + Poisson gravity) 2563 5123 no AMR base + one 4x level

20 40 60 80 100 120 number of GPUs 20 40 60 80 100 120 zones/ s updated

StarLord GPU performance

OLCF Summitdev

MHD – Algorithm

Assumes perfectly conducting fluid Only electric fields induced by motion of magnetized fluid

Miniati et al. 2011

Numerical schemes must ensure ∇ ∇ ∇ · B B B = 0 Magnetic field defined at face center Electric field at cell edges updates it

MHD port to Castro

Integrating MHD solver from Nyx (cosmology code) Support general EOS Add species Coupled with self-gravity conservative form Verification Shock tube test problem solved using 256 and 800 grid cells at t = 0.1 s.

White Dwarf mergers

Katz et. al. 2016

Presence of magnetic fields and effect on fluid instabilities could drive a hotspot into a detonation Include MHD in WD Merger simulation Continue with WD merger calculations Study feasibility of thermonuclear detonation Explore different initial models

◮ He layer ◮ CO + He mergers

Investigate algorithmic improvements

◮ Well-balanced scheme

with rotation

◮ Self-consistent initial

conditions

Timeline for next year

• Sept. 2018 – Verification and
• ptimization of MHD solver
• Oct. 2018 – Explore WD merger

initial models

• Jan. 2018 – MHD solver with

gravity tested

• Apr. 2019 – WD merger

investigation of self-consistent initial conditions

• Summer. 2019 – WD merger

simulations with MHD and additional physics Other work Contributing on GPU efforts Other planned research events BNL GPU Hackathon, Sept. 2018 SIAM CSE Minisymposium presentation, Feb. 2019